This creates two different profiles on your local machine, but when you visit the same website with both instances (say, you want to appear as two different persons in a chat), still both instances use the same circuit and therefore, using these two instances, both instances come from the same exit node, and so the target web-server will see the same IP-addresses from both instances. So, the target still knows that your two instances belong to the same physical person.
– Hubert SchölnastMay 10 at 8:24